How severe is CVE-2025-27157?

CVE-2025-27157 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2025-27157 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-27157?

CVE-2025-27157 affects Joinmastodon Mastodon. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-27157?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-27157 have an EU (EUVD) identifier?

Yes. CVE-2025-27157 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-5448.

When was CVE-2025-27157 published?

CVE-2025-27157 was published on 2025-02-27 and last updated on 2026-06-17.

CVE-2025-27157

CVE-2025-27157 is a medium-severity vulnerability in Joinmastodon Mastodon with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-770.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
EPSS exploit prediction: 0% (26th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-5448
Weakness: CWE-770
Affected product: Joinmastodon Mastodon
Published: 2025-02-27
Last modified: 2026-06-17

Description

Mastodon is a self-hosted, federated microblogging platform. Starting in version 4.2.0 and prior to versions 4.2.16 and 4.3.4, the rate limits are missing on `/auth/setup`. Without those rate limits, an attacker can craft requests that will send an email to an arbitrary addresses. Versions 4.2.16 and 4.3.4 fix the issue.

Frequently asked questions

What is CVE-2025-27157?: Mastodon is a self-hosted, federated microblogging platform. Starting in version 4.2.0 and prior to versions 4.2.16 and 4.3.4, the rate limits are missing on `/auth/setup`. Without those rate limits, an attacker can craft requests that will send an email to an arbitrary addresses. Versions 4.2.16 and 4.3.4 fix the issue.
How severe is CVE-2025-27157?: CVE-2025-27157 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2025-27157 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-27157?: CVE-2025-27157 affects Joinmastodon Mastodon. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-27157?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-27157 have an EU (EUVD) identifier?: Yes. CVE-2025-27157 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-5448.
When was CVE-2025-27157 published?: CVE-2025-27157 was published on 2025-02-27 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*

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